1. Field of the Invention
The present invention generally relates to an exposure control device for a camera, and more particularly to an exposure control device for a camera capable of controlling camera exposure by means of light measuring output obtained and stored prior to an actual exposure. Such an exposure control is necessitated in case that an optimum exposure control is desired with respect to a main object located at a particular point within an area to be photographed, e.g., at a corner of the rectangular scene area to be photographed.
2. Description of the Prior Art
In case that, for example, one desires to photograph a composition with the main object located at a corner of the rectangular scene area to be photographed, exposure control is not generally optimum with respect to the main object since an automatic exposure control camera is so designed to control exposure in response to an averaging or a center-weighted light metering output determined subsequent to the camera release operation with respect to the whole area to be photographed.
For the purpose of achieving an optimum exposure control with respect to the main object as in the above case, prior art cameras are provided with a manually operable switch for storing a light measuring output prior to the camera release operation. This is disclosed, for example, in U.S. Pat. No. 3,756,131. The method of photography using such a camera comprises: a first step to operate the manually operable switch with the camera close to the main object so that substantially the whole acceptance angle effective for light measuring may be occupied by the main object, and the value of the stored light measuring output may thereby be determined with respect to the main object only; and a second step where the camera is returned to a position for making the desired composition and the camera release operation is actually carried out so that the exposure control may be determined by the stored light measuring output.
The above method, however, is only possible in case of a camera which is designed to control exposure in response to a TTL light measuring output obtained with the aperture at its initial aperture size, e.g., a fully open aperture size.
Moreover, there is a camera of the type in which the exposure is controlled by a TTL light measuring output obtained after the initiation of the aperture stopping-down motion from its fully open aperture size. In this type of camera, the above mentioned method is not applicable since any reliable light measuring output is not obtainable until the aperture stopping-down motion actually begins subsequent to the actual camera release operation, thereby making the above mentioned first step impossible.